Well, I mostly know the theory behind them, I've made small ones.... Dam I wish I could draw a picture in paint or something then you could see what I'm thinking.... Stupid mac. And i Can't draw one at school cuz its friday.... I'll get a pic then you can see.

EDIT::Got a Pic! (now if only I can figure out how to insert...... Voila!)

Ok so essentially this is a top view. The bar in the middle is the axel, Attached to the red gear (wont be red). This gear can attach to whatever I want to spin it. Probably a bike. The grey around it is the magnets, and the big brown square is the base. The black bars on either end are the ball bearings that attach it to the base On either side (This brown rectangles) Are where I'me going to wrap the wire.

So the question is, Is it better to put the wire on either side or get a pipe to completally surround it? and how should it be wrapped? 2 continuous loops on either side, or a bunch of small connected loops?